1. Field of the Invention
The present invention relates to an information management system and a method therefor. More specifically, the present invention relates to an information management system for managing mutually related information items intended for use in process schedule control by way of example, each information item may be assigned a unique identifier.
2. Description of the Related Art
In recent years, the amount of data stored in database systems has increased dramatically, and the amount of information indicating relationships among the stored data items has also increased dramatically
As an example, in process schedule control, an operational environment that involves man-machine interactions in four-dimensional events (including time) must be managed. As examples of relationships between object activities and men or machines for processing activities, there are a tree structure pattern, representing an organization, and a work flow, representing a sequence of processes. The activities are within constraints of time, cost, quality, company's rules, procedures, etc. It is desirable that the complex operational environment be defined and managed with as little information as possible in an efficient manner.
Information required for process schedule control includes information on the organization of a company as an organization for performing work and information on individual working processes. Of the information on the organization of the company, rank (upper and lower) relationships among workers are important. Of the information on working processes, time-sequential (before and after) relationships among the working processes are important.
In a conventional tree structure, however, links representing rank (up and down) relationships exist, but there is no link representing before and after relationships between information items of the same rank in the tree structure. That is, the structure of pointers indicating mutual relationships between information items is one dimensional, and no two-dimensional pointer is implemented.
A tree structure using bidirectional (upward and downward) pointers requires twice as many pointers as a tree structure using unidirectional (upward or downward) pointers. Therefore, many of conventional tree structures have downward pointers but not upward pointers. With tree structures only having such downward pointers, downward data retrieval from the tree's root to its leaves can be performed, but upward retrieval is impossible.
The reason why the pointers are generally of one dimension and in many cases there are only unidirectional pointers is to decrease the amount of data required to indicate relationships among items of information. Setting pointers of two dimensions of up, down, before and after, i.e., in four directions, to information required for the above-mentioned process schedule control becomes increasingly difficult as the amount of information required actually increases.